Morphology modulated growth of bismuth tungsten oxide nanocrystals

Two kinds of bismuth tungsten oxide nanocrystals were prepared by microwave hydrothermal method. The morphology modulation of nanocrystals synthesized with precursor suspension's pH varied from 0.25 (strong acid) to 10.05 (base) was studied. The 3D flower like aggregation of Bi2WO6 nanoflakes was synthesized in acid precursor suspension and the nanooctahedron crystals of Bi3.84W0.16O6.24 were synthesized in alkalescent precursor. The dominant crystal is changed from Bi2WO6 to Bi3.84W0.16O6.24 when the precursor suspension changes from acid to alkalescence. The growth mechanisms of Bi2WO6 and Bi3.84W0.16O6.24 were attributed to the different solubility of WO42- and [Bi2O2]2+ in precursor suspensions with various pH. For the decomposition of Rhodamine B (RhB) under visible light irradiation (λ>400 nm), different morphology of Bi2WO6 crystal samples obtained by microwavesolvothermal process showed different photocatalytic activity. - Graphical abstract: The morphology modulation of bismuth tungsten oxide nanocrystals synthesized by microwave hydrothermal method with precursor suspension's pH varied from 0.25 (strong acid) to 10.05 (base) was studied. The 3D flower like aggregation of Bi2WO6 nanoflakes and nanooctahedron crystals of Bi3.84W0.16O6.24 were prepared. The growth mechanisms of Bi2WO6 and Bi3.84W0.16O6.24 were attributed to the different precipitation ability and solubility of H2WO4 and Bi(OH)3 in precursor suspensions with various pH. The photocatalytic evaluation, via the decomposition of Rhodamine B (RhB) under visible light irradiation (λ>420 nm), reveals that nanocrystalline Bi2WO6 samples obtained in different condition exhibit different photocatalytic activities which depend on pH value of the precursor suspensions